Our project proposal focuses on the interaction of proteins with nucleic acids. High resolution structures provide insights into the atomic basis for processes in DNA replication, transcription, recombination and nucleic acid recognition. We have used the high flux A1/F1 and tunable F2 beamlines to solve several new structures that contribute to our understanding of these fundamental processes. Using Multiwavelength Anomalous Diffraction (MAD) at beamline F2 we recently completed the structure of T7 RNA polymerase complexed to a primer:template DNA and the RAG1 dimerization domain. In addition, we have also used anomalous diffraction by divalent metals to study the DNA polymerase I exonuclease active site. The high flux A1 and F1 beamlines have proven to be essential to improving the quality and extent of diffraction for our macromolecular crystals. In the last year we have solved the structures of the T7 RNA polymerase:DNA complex, bacteriophage RB69 gp45 (a DNA replication processivity factor), as well as the ROP, and RRE RNAs. Several other projects are currently in the process of being solved and include resolvase:DNA complex, and TAQ DNA polymerase I bound to a variety of polymerase active site substrates.